【单选题】
当发生切换掉话时,BSC向MSC发送clearrequest消息,该消息的原因是什么()
A、RADIOINTERFACEFAILURE
B、HANDOVERFAILURE
C、RADIOINTERFACEMESSAGEFAILURE
D、RADIOINTERFACEFAILUREREVERSIONTOOLDCHANNEL
A、RADIOINTERFACEFAILURE
B、HANDOVERFAILURE
C、RADIOINTERFACEMESSAGEFAILURE
D、RADIOINTERFACEFAILUREREVERSIONTOOLDCHANNEL